1. Field of the Invention
This invention generally relates to a scroll type fluid machine adapted to be used as a pump for a compressive fluid, a blower, a compressor or the like, and more particularly to a scroll fluid machine suitable for a compressor for compressing a refrigerant used in an air conditioner, a refrigerating apparatus or the like.
2. Description of the Related Art
There has been developed a scroll type fluid machine having a pair of scroll members cooperating with each other and widely used in various fields. In general, each scroll member has an end plate and a spiral scroll wrap or ridge projectingly formed on one surface of the end plate.
The scroll wrap of the scroll members are inserted in spiral grooves defined by the adjacent turns of the spiral wrap of the opposed scroll members so that they are arranged to form crescent chambers defined therebetween. The end faces of the scroll wrap of the scroll members sealingly contact the end plates of the scroll members. As the scroll members are moved relatively, the volumes of crescent working chambers defined between the scroll wraps vary. More specifically, as the scroll members, eccentrically arranged relative to each other, are revolved without rotating about their own axes, each working chamber is moved circumferentially and inwardly, reducing its volume. On the other hand, the reverse revolution of the scroll members without rotating around their own axes causes each working chamber to be moved circumferentially and outwardly, increasing its volume. These two processes provide the compression and expansion of the fluid in each working chamber. The scroll type fluid machine having this structure has the advantages that the variation of the driving torque is small and little fluid leaks from the working chambers.
The Japanese laid-open Patent Application No. 57-131,896 laid open on Aug. 14, 1982 discloses a scroll compressor for compressing refrigerant used in an air conditioner or in a refrigerating apparatus.
The scroll compressor has a container in which are sealingly housed a pair of scroll members and a driving motor disposed thereover in a compact manner. One of the scroll members is fixed to the sealed container and the other one (hereinafter referred to as the "movable scroll member") is provided thereabove, that is, at the side of the driving motor so as to be revolvable abound the axis of the fixed scroll member. A crank shaft extending from and driven by the driving motor is supported by a frame which divides the interior of the container into a driving-motor side chamber and a compressor side chamber, and comprises a crank pin rotatably extending through the movable scroll member and a lower end portion rotatably supported by the fixed scroll member. In the outer periphery of the fixed scroll member is formed an intake port for sucking in a refrigerant gas which port communicates with the beginning portion of a groove defined between the extreme outer portion of the scroll wrap of the fixed scroll member and the inner wall of the fixed scroll member.
When the crank shaft is rotated by the driving motor, the movable scroll member is revolved without rotating around its own axis, together with the crank pin. The refrigerant gas sucked in from the intake port is compressed in each working chamber defined between the movable scroll member and the fixed scroll member as its volume is decreased and arrives at the innermost portion of the groove defined between the adjacent lateral walls of the scroll wrap of the fixed scroll member in the most compressed state. The compressed refrigerant gas is discharged from the upper portion of the container through discharge duct formed in the central portion of the fixed scroll member.
The discharge duct has an axial bore formed in the generally central portion of the end plate of the fixed scroll member and communicating with the innermost working chamber, a radial bore radially extending through the end plate and having one end communicating with the axial hole, and another axial bore extending in the outer peripheral portion of the end plate and communicating with the other end of the radial hole.
In this connection, three machining processes are required to form the complicated discharge duct in the fixed scroll member in this conventional scroll compressor, increasing the manufacturing cost. The end plate of the fixed scroll member must be made thick to form the radial bore therein.
Further, it is necessary that discharge duct formed on the fixed scroll member communicate with a duct formed on the frame so that the compressed refrigerant gas is discharged from the upper portion of the container. Since the frame and the fixed scroll member which sandwich the movable scroll member cannot have large contact areas in view of their structure, a sufficient sealing area for effecting the sealing between both discharge ducts cannot be provided, it is feared that the refrigerant gas under high pressure leaks between the frame and the fixed scroll member toward the intake port.